1. Field of the Invention
The present invention relates to a heater member for mounting an object of heating, and to a substrate processing apparatus using the same.
2. Description of the Background Art
Various heaters have been proposed for mounting and heating objects of heating. For example, a heater containing, as a main component, aluminum nitride having high thermal conductivity and high thermal uniformity in the heater, and a heater using alumina, which is inexpensive, have been known. In order to efficiently heat the objects of heating, various shapes and the like have been proposed for such heaters.
An object of the present invention is to provide a heater member for mounting an object of heating and a substrate processing apparatus using the same, that can reduce power to be fed to the heater necessary for heating to a prescribed temperature and that can heat the object of heating with higher efficiency.
According to the present invention, the heater member for mounting an object of heating is characterized in that at least a part of a surface other than an object mounting surface is mirror-finished.
The inventors made various attempts to realize efficient heating of the object, and have found that surface roughness of the heater on which the object is mounted has a significant influence on the heating of the object.
For example, assume that a power is fed to a resistance heater embedded in an insulator such as ceramic to generate heat. The Joule""s heat generated thereby is transmitted through the ceramic to the object, and heats the object. Transmission of the heat to the object of heating is attained by heat transfer, radiation and convection.
At a surface other than the object mounting surface of the heater member, however, the heat is transmitted to the peripheral portion, i.e. the surroundings, by radiation and convection. Therefore, it is necessary for the heater member to generate, by Joules heat, such a quantity of heat that is the sum of the heat for heating the heater member itself, the heat for heating the object and the heat transmitted to the peripheral portion. As a method of reducing the quantity of heat transmitted to the peripheral portion among the required heat quantity, the inventors have found that it is effective to mirror-finish at least a part of the surface other than the object heating surface of the heater member.
More specifically, Joule""s heat generated by the resistance heater is transmitted through the ceramic and heats the ceramic itself. Thereafter, when the heat is radiated to the peripheral portion and the ceramic surface is mirror-finished, it has been found that the heat that is to be radiated at the surface of the ceramic is reflected and again taken into the ceramic. Thus, the heat radiated outward from the heater member reduces, enabling efficient heating of the object.
Preferably, in the heater member for mounting the object, at least a part of the surface opposite to the object mounting surface is mirror-finished.
Assuming that the heater member is of the same temperature entirely, the effect attained by the mirror-finishing is in proportion to the mirror-finished area. Thus, when the surface opposite to the object mounting surface is mirror-finished, a large mirror-finished area can be ensured, and the quantity of heat radiated from the heater member to the outside can significantly be reduced.
Therefore, all the surfaces other than the object mounting surface of the heater member may be mirror-finished. This can maximize the effect of mirror-finishing.
In the heater member for mounting an object described above, the surface roughness of the mirror-finished portion is Raxe2x89xa60.2 xcexcm.
The surface roughness is set to Raxe2x89xa60.2 xcexcm, as the ratio of reflection of the heat generated in the heater at the surface lowers and the quantity of radiation at the peripheral portion of the heater member becomes relatively large when the surface roughness exceeds 0.2 xcexcm.
Preferably, in the heater member for mounting an object of heating, the surface roughness of the mirror-finished portion is Raxe2x89xa60.05 xcexcm.
When the surface roughness is made at most 0.05 xcexcm, the amount of radiation to the peripheral portion of the heater member can more significantly be reduced.
The surface roughness of the object mounting surface is not specifically limited. When the object mounting surface is mirror-finished, for example, adhesion with the object of heating improves, and therefore, heat transmission through contact increases as compared with heat transmission by radiation. When the surface roughness is not at the level of mirror-finish, the quantity of heat transmission attained by heat transfer lowers, while the quantity of heat transmitted through radiation increases. Therefore, the surface roughness of the object mounting surface does not have much influence as compared with the surfaces other than the object mounting surface.
When the object of heating is in tight contact with the heater member, it is preferred that the object mounting surface is also mirror-finished, with the surface roughness being Raxe2x89xa60.2 xcexcm (more preferably, Raxe2x89xa60.05 xcexcm). Here, when the object mounting surface is mirror-finished, contact area between the heater member and the object increases, and therefore heat can be transmitted more efficiently from the heater member to the object.
When it is the case that the object is simply placed (positioned) on the heater member and the substrate mounting surface is mirror-finished, reflection of Joule""s heat, that is the effect of the present invention, occurs, and hence transmission of heat to the object will be hindered.
Therefore, in order to attain tight contact between the object and the heater member, the heater member and the object of heating may brought into tight contact by mechanically pressing the protruding surfaces of these two by means of a clamp at an outer peripheral portion, or by electrostatic chuck, for example.
In the heater member for mounting an object of heating described above, the object includes a semiconductor wafer and a liquid crystal substrate.
Thus, efficient heating of a semiconductor wafer or a liquid crystal substrate becomes possible, and processing such as film formation on the substrates can be done efficiently.
The substrate processing apparatus in accordance with the present invention employs the heater member for mounting the object of heating described above, and heats and processes, as the object of heating, a semiconductor wafer or a liquid crystal substrate.
Thus, the semiconductor wafer or a substrate for liquid crystal can be heated efficiently as described above, and hence, a substrate processing apparatus can be provided that enables efficient processing such as film formation on such substrates.
In the present invention, the material of the heater is not particularly limited. For example, a heater having a resistance heater embedded in an insulator such as ceramic, or a heater having a heating body such as nichrome covered by a metal sheet may be used. Various heaters may be selected dependent on the intended application.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.